Garage door panels for overhead doors have been made of wood and particle board materials. Such panels are inherently moisture-absorbent and limited in length because of increased weight and the tendency to warp. As a consequence frequency repainting or waterproofing is required. The use of reinforcing ribs to inhibit warping has been proposed but this adds substantial weight and expense.
Door panels for commercial use have been hollow with walls of metal or rigid plastic materials such as fiberglass, and such doors have sometimes been provided with relatively shallow ribs to prevent flexing or "oil canning" of the walls. These panels are sometimes provided with a core of insulating material. Such door panels of which I am aware have certain disadvantages due in part to the fact that they have been manufactured by piece-by-piece methods which are time-consuming and expensive and the construction does not lend itself to manufacture by a continuous method.
Other disadvantages include the excess weight of metal doors, the brittleness and lack of durability of certain plastic materials, and the expense of inserting the insulating core material.